“The Duke and Duchess of Cambridge are very pleased to announce that The Duchess of Cambridge is expecting their second child,” tweeted Clarence House.

A statement from Kensington Palace said that the Queen and members of the royal family are “delighted with the news”.

As with her pregnancy with Prince George, the Duchess is suffering from acute morning sickness – hyperemesis gravidarum. She is being treated inside Kensington Palace this time, rather than a private hospital where press had previously waited outside for updates.

“We’re immensely thrilled, it’s great news, early days but I’m hoping that things settle down, she feels a bit better,” said Prince William today during an official visit to open the Dickson Poon University of Oxford China Centre Building. His wife pulled out of the engagement due her sickness.

“She’s feeling ok,” he continued. “It’s been a tricky few days, week or so. I’m going to go back and look after her now.”

Kensington Palace said the Duchess’s attendance at forthcoming events would be decided on a “case-by-case” basis.

The Duchess had not yet passed her 12-week point, but the couple decided to make an announcement because of forthcoming public engagements which are now uncertain.

The new baby will be the fourth in line to the throne. He or she will not become a monarch, assuming the same role as Prince Harry.